You have designed and constructed a solenoid to produce a magnetic field equal in magnitude to that of the Earth (5.0 10-5 T). If your solenoid has 450 turns and is 38 cm long, determine the current you must use in order to obtain a magnetic field of the desired magnitude.

 I = 5.3 102 A

Explanation:

The magnetic field created by a solenoid is

            B = μ₀ N/L  I

Where B  the magnetic field, N the number of turns, L the length of the solenoid and I the current flowing

           I = B L / μ₀ N

Let's reduce to the SI system

         L = 38 cm = 0.38 m

Let's calculate

         I = 5.0 10⁻⁵ 0.38 / (450 4π 10⁻⁷)

        I = 5.3 102 A

the answer is ampere

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